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991.
采用XRD表征了水蒸气和磷联合改性的HZSM-5沸石分子筛的结构.通过NH3-TPD和N2吸附脱附研究了样品的酸性和比表面.采用正庚烷的裂化反应研究了样品的裂化活性,研究结果表明,磷改性样品与母体样品相比,经过水蒸气处理后显示出较高的酸量和正庚烷裂化活性.上述结果首次用模型簇和计算量子化学方法进行了解释.采用Gaussian94软件包和PM3半经验量子化学方法对模型簇进行了全优化和频率分析.计算结果显示磷改性后样品的脱铝补硅反应热大于母体样品脱铝补硅反应热,从而显示出磷对骨架的稳定化作用. 相似文献
992.
2-(8-羟基喹啉-5-磺酸-7-偶氮)-1,8-二羟基-3,6-萘二磺酸与牛血清白蛋白的相互作用 总被引:5,自引:0,他引:5
用平衡透析法和分光光度法研究了 2 (8 羟基喹啉 5 磺酸 7 偶氮 ) 1,8 二羟基 3,6 萘二磺酸与牛血清白蛋白 (BSA)在酸性溶液中的结合反应 ,认为 8Q5SAC与BSA之间的结合力是以静电引力为主的非共键作用力 ,并探讨了其结合模型。在 2 98K下 ,测得这一反应的最大结合数为 35~ 40 ,结合常数为 6 .1× 10 5L mol。还研究了溶液基本条件如酸度和离子强度等对 8Q5SAC与牛血清白蛋白分子复合物形成的影响 ,在pH =3.34条件下 ,标准工作曲线的线性范围为 0 .2 0~ 46 .90mg L。 相似文献
993.
The static polarizabilities and the second-order hyperpolarizabilities of a series of tri-nuclear metal cluster models MS4(M′PPh3)2(M′PPh3)(M=Mo,W;M′=Cu,Ag,Au)have been calculated within the first-principle theoretical framework. The model clusters have two fragments of rhombic units and it is the charge ransfer from one of these moieties to the other that is responsible for nonlinear optical property. This kind of electronic delocaization, differentiated from that of planar π-system, is very interesting and is worthy for further investigation. 相似文献
994.
The approximate expressions have been obtained to calculate the electrical double layer energy and force between two spherical colloidal particles based on the improved Derjaguin approximation. Results for identical spheres interacting under constant surface potential, constant surface charge are given. Comparison of present results with numerical results calculated by Carnie and Chan is made. The expressions are found to work quite well for the constant surface potential case, and for the constant charge case, we make correction for the expressions. The results given are satisfactory providedkh0.4. 相似文献
995.
996.
We present a method for computing classical Newtonian trajectories that minimize the path length or transit time from reactant
to product. Our approach is based on a generalization of the fast-marching method, which allows us to construct the solution
of the Hamilton-Jacobi equation for the action that optimizes the desired quantity. The resulting “reactive paths” can be
interpreted as reaction coordinates but, unlike more conventional choices, they contain dynamical information about the chemical
system of interest. 相似文献
997.
Sung Woo Moon Gun-Dae Lee Seong Soo Park Seong-Soo Hong 《Reaction Kinetics and Catalysis Letters》2004,82(2):303-310
Catalytic combustion of chlorobenzene over supported vanadium oxides has been investigated. TiO2 was prepared by the sol-gel method from titanium isopropoxide. The supported vanadium oxide catalysts have been prepared
by precipitation-deposition and impregnation method and characterized by XRD, FT-Raman and TPR. In the VOx/TiO2catalysts prepared using the impregnation method, when vanadium loading reaches 3 wt.%, the activity shows a maximum. However,
in the VOx/TiO2catalysts prepared by precipitation-deposition, when vanadium loading reaches 7 wt.%, the activity shows a maximum. This result
suggests that the precipitation-deposition can yield a higher metal loading on the support and a high dispersion compared
to the impregnation method.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
998.
John H.T Luong Caide Xiao Š.Mircea Leabu Xiaolan Li Shashi Uniyal Bosco M.C Chan 《Analytica chimica acta》2004,501(1):61-69
Electric cell-substrate impedance sensing (ECIS) was applied to assess the structure-function of α2β1 integrin, receptor for collagen and laminin. On collagen-coated gold electrodes, expression of this integrin on human rhabdomyosarcoma (RD) cells (RDX2C2) yielded a five-fold increase in resistance when compared with mock transfected RD (RDpF) cells (34.5±5.2 versus 6.5±0.8 Ω/cell). An intermediate level of 16±2 Ω/cell was measured upon expression of an α2β1 mutant that lacked the α2 cytoplasmic domain (RDX2CO). On laminin, the resistance measured for RDX2C2 cells was also higher but only twice that of RDpF cells at 71±4 and 37±4 Ω/cell, respectively. In comparison, RDX2CO cells (38±4 Ω/cell), exhibiting no enhanced adhesive function, yielded a similar result to that of RDpF cells. On fibronectin, RDX2C2 and RDpF cells, exhibiting comparable levels of adhesion, were similar in resistance measurements at 85±5and 89±7 Ω/cell, respectively. It has been shown that deletion of α2 cytoplasmic domain results in dysregulated recruitment of the α2β1 mutant to focal adhesion complexes that mediate binding of fibronectin. RDX2CO cells on fibronectin, exhibiting reduced adhesive function, was associated with noticeably lower resistance (60±4 Ω/cell). Monitoring electroporation of the RD plasma membrane also indirectly validated cell attachment as reflected by the resistance measured. Results from this study demonstrated the potential of ECIS for study of the structure-function of βl integrin adhesion receptors. 相似文献
999.
采用水热法合成了系列Ce1-XMnXO2-a-T(X=0.0,0.1,0.2,0.3,0.5,0.7,0.9,1.0;T表示焙烧温度),T=500,650,800 ℃)复合氧化物催化剂用于甲烷的催化燃烧。通过XRD、N2吸/脱附、TG-DSC、UV-Vis-DRS和TPR表征手段研究了不同组成催化剂的物理化学性质及其对甲烷催化燃烧活性。结果表明,在500 ℃焙烧的情况下Mn进入CeO2晶格形成均相固溶体催化剂的最大取代值为0.7,而当Mn继续增加时则出现Mn2O3晶相偏析,同时各催化剂具有较高的比表面积;随着焙烧温度的升高,进入CeO2晶格的Mn最大取代值逐渐减少,650和800 ℃时分别为0.5和0.3,且比表面积相应降低。Ce1-XMnXO2-a-800催化剂的还原行为大致呈现三阶段,即为Mn2O3 → Mn3O4的还原(340~420 ℃),Mn3O4 → MnO的还原(420~480 ℃)和体相氧化铈的还原(700~900 ℃),且Mn的引入整体上提高了催化剂的可还原能力。甲烷催化燃烧活性评价结果表明,比表面积并非影响催化剂活性的主要因素,影响催化剂甲烷催化活性的主要因素为催化剂的组成、可还原能力和焙烧温度;而其中以Ce0.3Mn0.7O2-a-800催化剂表现出较高的甲烷催化燃烧活性,在甲烷转化率为10%和90%时的温度分别为430 和613 ℃。进一步考察Ce0.3Mn0.7O2-a在不同温度(500、650、800和1 000 ℃)焙烧后的催化活性表明,随着焙烧温度的提高催化剂催化活性降低。 相似文献
1000.
镀金层识别及其厚度测定的X—荧光强度比值法 总被引:3,自引:0,他引:3
利用Au原子在X射线激发下所发射的Lβ线和M线的强度比值识别样品是镀金还是K金,同时利用这个比值测定镀金层的厚度,镀金层厚度的测定范围为0~4μm,测定值与标定值的相对误差小于15%。 相似文献